Simulation Parameters

Introduction

This table defines the configuration settings for the simfish simulation environment. Note that distances are measured in pixels (the default values are based on a ratio of 10 pixels = 1 mm).

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1. Global Simulation Settings

General constraints for the simulation engine and time-stepping.

Name	Meaning	Example Value	Data Type	Optional
test_sensory_system	Enables diagnostic mode for visual inputs	false	Boolean	No
max_sim_steps_per_episode	Max steps before an episode ends	1000	Integer	No
phys_steps_per_sim_step	Physics model sub-steps for each simulation step	100	Integer	No
sim_step_duration_seconds	Real-world time delta per step in seconds	0.2	Float	No

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2. Arena

Defines the physical boundaries and lighting conditions.

Name	Meaning	Example Value	Data Type	Optional
width / height	Arena dimensions (pixels)	5000	Integer	No
dark_fraction	Fraction of the arena that is dark	0.0	Float	No
light_gradient	Steepness of light-to-dark transitions (pixels)	20	Integer	No
dark_gain	Dark region illumination fraction	0.1	Float	No
light_decay_rate	Rate at which light intensity decreases over distance	0.01	Float	No
uv_object_intensity	Multiplier for UV-reflective objects	1.2	Float	No
bottom_intensity	Intensity of light scattering at the bottom of the arena	60.0	Float	No
sediment_sigma	Standard deviation for sediment texture	5.0	Float	No
water_uv_scatter	UV scattering coefficient for water	0.1	Float	No
wall_bounce	If true, fish reflects off walls	false	Boolean	No

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3. Fish

Parameters governing the physical body and the visual system of the agent.

[Image of larval zebrafish visual field and eye vergence]

Name	Meaning	Example Value	Data Type	Optional
mouth_radius	Size of prey capture area (pixels)	2.0	Float	No
head_radius	Radius of fish head (pixels)	2.5	Float	No
tail_length	Physical tail length (pixels)	41.0	Float	No
elevation	Height of the fish’s above the bottom (pixels)	50	Integer	No
deterministic_action	If true, fish actions are deterministic, based on mean value	false	Boolean	No

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4. Eyes and vision

Parameters governing the visual system of the agent.

Name	Meaning	Example Value	Data Type	Optional
verg_angle	Eye vergence angle (degrees)	77.0	Float	No
visual_field	Total degrees of vision per eye	163.0	Float	No
biasx	Horizontal offset of each eye from the midline (pixels)	2.5	Float	No
shot_noise	If true, adds shot noise to visual input	true	Boolean	No
uv_photoreceptor_rf_size	Size of UV photoreceptor receptive fields (radians)	0.0133	Float	No
red_photoreceptor_rf_size	Size of red photoreceptor receptive fields (radians)	0.0133	Float	No
sz_rf_spacing	Spacing of RFs in the strike zone (radians)	0.04	Float	No
sz_size	Size of the strike zone (radians)	1.047	Float	No
sz_oversampling_factor	Oversampling factor PRs in the strike zone	2.5	Float	No
sz_edge_steepness	Steepness of the strike zone edge	5.0	Float	No
viewing_elevations	Angles of bottom viewing (degrees)	[50, 75]	List	No

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5. Capture swim

Name	Meaning	Example Value	Data Type	Optional
permissive_time_fraction	Fraction of time within the bout that still allows capture	0.5	Float	No
permissive_angle	Angle within which capture is allowed (degrees)	0.785	Float	No
energy_cost_scaling	Multiplier for energy cost during capture	5	Float	No

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6. Prey

Behavioral variables for prey items (paramecia)

Name	Meaning	Example Value	Data Type	Optional
radius	Collision radius of prey	1.0	Float	No
num	Number of prey items	30	Integer	No
sensing_distance	Distance at which prey can sense the fish (pixels)	100	Float	No
max_turning_angle	Maximum angle prey can turn (radians)	0.15	Float	No
cloud_num	Number of prey clouds (zero for even distribution)	3	Integer	No
p_slow	Probability of slow gait	0.8	Float	No
p_fast	Probability of fast gait	0.2	Float	No
p_escape	Probability of escape gait if in range	0.3	Float	No
p_switch	Probability of switching gait	0.05	Float	No
p_large_turn	Probability of large turn behavior	0.04	Float	No
velocity_slow	Speed during slow movement (px/sec)	10.0	Float	No
velocity_fast	Speed during fast movement (px/sec)	20.0	Float	No
velocity_jump	Speed during a prey escape burst (px/sec)	1800	Integer	No
reproduction_mode	If true, prey can reproduce	false	Boolean	No
birth_rate	Probability of new prey spawning	0.002	Float	No
cloud_region_size	Size of the prey clouds	200	Integer	No
safe_duration	Minimal prey lifespan (steps)	100	Integer	No
p_death	Probability of prey death	0.001	Float	No

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7. Predator

Behavioral variables for predator items

Name	Meaning	Example Value	Data Type	Optional
radius	Hitbox/shadow radius of the predator	64	Integer	No
velocity	Movement speed of the predator (px/sec)	90	Float	No
immunity_steps	Steps fish is safe early in the episode	200	Integer	No
distance_from_fish	Initial distance from the fish (px)	180.0	Float	No
epoch_num	Number of predator attack epochs	5	Integer	No
epoch_duration	Duration of each epoch (steps)	50	Integer	No
probability_per_epoch_step	Probability of predator action per step during epochs	0.07	Float	No
stim_file	Path to predator stimulus location data	./analysis/...	String	Yes

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8. Salt source

Salt gradient configuration

Name	Meaning	Example Value	Data Type	Optional
enabled	Whether salt gradients are enabled	true	Boolean	No
concentration_decay	concentration decay constant (1/pixels)	0.002	Float	No

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9. Rewards

Name	Meaning	Example Value	Data Type	Optional
predator_caught	Penalty for being eaten	-2	Integer	No
predator_avoidance	Reward for avoiding predators	2	Integer	No
consumption	Reward for catching prey	3	Integer	No
energy_use_factor	Factor for translating energy use to negative rewards	10	Integer	No
wall_touch	Penalty for touching walls	-2	Integer	No
salt_factor	Factor for salt concentration influence	-0.05	Float	No

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10. Energy

Name	Meaning	Example Value	Data Type	Optional
distance_factor	Energy cost per unit of movement	0.00023	Float	No
angle_factor	Energy cost per degree of turning	0.0001	Float	No
baseline	Passive energy loss per step	0.00002	Float	No